In Key West the Truman museum is worthwhile. Lots and lots of shops for your wife and daughters.

We didn't go into Cozumel proper. Went to Playa del Carmen for the Tulum ruins tour. Big waste as we had a tour guide how told us absolutely nothing about the ruins. Next time, we'll do Cozumel proper. Have friends who rented a jeep for the day and did their own tour.